Flexible renal nerve ablation devices and related methods of use and manufacture

ABSTRACT

Medical devices for renal nerve ablation are disclosed. An example medical device for renal nerve ablation may include a catheter shaft having a distal region. The device may include an expandable member coupled to the distal region, a flexible circuit assembly coupled to the expandable member, and a pressure sensor disposed along the expandable member and positioned adjacent to the flexible circuit assembly. The flexible circuit assembly may include one or more pairs of bipolar electrodes and a temperature sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to U.S.Provisional Application Ser. No. 61/890,740, filed Oct. 14, 2013, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods forusing and manufacturing medical devices. More particularly, the presentdisclosure pertains to medical devices and methods that relate to renalnerve ablation.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

SUMMARY

Medical devices and methods for making and using medical devices aredisclosed herein. One such exemplary medical device may include a renalnerve ablation device that has a catheter shaft with a distal region. Inaddition, the device may include an expandable member coupled to thedistal region. The device may further include a flexible circuitassembly coupled to the expandable member, such that the flexiblecircuit assembly may include one or more pairs of bipolar electrodes anda temperature sensor. The device may further include a pressure sensordisposed along the expandable member and positioned adjacent to theflexible circuit assembly.

Another exemplary medical device for renal nerve ablation may include acatheter shaft having a distal region. A compliant balloon may becoupled to the distal region of the catheter shaft. One or more pairs ofbipolar electrodes may be coupled to the compliant balloon. Further, thedevice may include one or more temperature sensors and one or morepressure sensors that are each coupled to the compliant balloon.

An exemplary method for ablating renal nerves may include providing arenal nerve ablation device that includes a catheter shaft having adistal region. The device may further include a compliant ballooncoupled to the distal region, and one or more pairs of bipolarelectrodes coupled to the compliant balloon. Further, the device mayinclude one or more temperature and pressure sensors that are eachcoupled to the compliant balloon. The method may also include advancingthe renal nerve ablation device through a blood vessel to a positionwithin a renal artery. Further, the method may include expanding thecompliant balloon, which may be followed by sensing contact between thecompliant balloon and the renal artery with the one or more pressuresensors. Still further, the method may include activating at least oneof the one or more pairs of bipolar electrodes.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present invention.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thepresent disclosure and together with the description, serve to explainthe principles of the disclosure.

FIG. 1 is a schematic view illustrating an exemplary renal nerveablation system, according to some embodiments of the presentdisclosure.

FIG. 2 illustrates a related art renal nerve ablation device within avessel.

FIG. 3 illustrates an exemplary renal nerve ablation device, inaccordance with the present disclosure.

FIG. 4 illustrates another exemplary renal nerve ablation device, inaccordance with the present disclosure.

DETAILED DESCRIPTION

The following description should be read with reference to the drawings,which are not necessarily to scale, wherein like reference numeralsindicate like elements throughout the several views. The detaileddescription and drawings are intended to illustrate but not limit theclaimed invention. Those skilled in the art will recognize that thevarious elements described and/or shown may be arranged in variouscombinations and configurations without departing from the scope of thedisclosure. The detailed description and drawings illustrate exampleembodiments of the claimed invention.

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about”, in thecontext of numeric values, generally refers to a range of numbers thatone of skill in the art would consider equivalent to the recited value(i.e., having the same function or result). In many instances, the term“about” may include numbers that are rounded to the nearest significantfigure. Other uses of the term “about” (i.e., in a context other thannumeric values) may be assumed to have their ordinary and customarydefinition(s), as understood from and consistent with the context of thespecification, unless otherwise specified. The recitation of numericalranges by endpoints includes all numbers within that range, includingthe endpoints (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise. It isnoted that references in the specification to “an embodiment”, “someembodiments”, “other embodiments”, etc., indicate that the embodiment(s)described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments, whether or not explicitlydescribed, unless clearly stated to the contrary. That is, the variousindividual elements described below, even if not explicitly shown in aparticular combination, are nevertheless contemplated as beingcombinable or arrangable with each other to form other additionalembodiments or to complement and/or enrich the described embodiment(s),as would be understood by one of ordinary skill in the art.

Certain treatments are aimed at the temporary or permanent interruptionor modification of select nerve function. In some embodiments, thenerves may be sympathetic nerves. One example treatment is renal nerveablation, which is sometimes used to treat conditions such as or relatedto hypertension, congestive heart failure, diabetes, or other conditionsimpacted by high blood pressure or salt retention. The kidneys produce asympathetic response, which may increase the undesired retention ofwater and/or sodium. The result of the sympathetic response, forexample, may be an increase in blood pressure. Ablating some or all ofthe nerves running to the kidneys (e.g., disposed adjacent to orotherwise along the renal arteries) may reduce or eliminate thissympathetic response, which may provide a corresponding reduction in theassociated undesired symptoms (e.g., a reduction in blood pressure).

Some embodiments of the present disclosure relate to a power generatingand control apparatus, often for the treatment of targeted tissue inorder to achieve a therapeutic effect. In some embodiments, the targettissue is tissue containing or proximate to nerves. In otherembodiments, the target tissue is sympathetic nerves, including, forexample, sympathetic nerves disposed adjacent to blood vessels. In stillother embodiments the target tissue is luminal tissue, which may furthercomprise diseased tissue such as that found in arterial disease.

In some embodiments of the present disclosure, the ability to deliverenergy in a targeted dosage may be used for nerve tissue in order toachieve beneficial biologic responses. For example, chronic pain,urologic dysfunction, hypertension, and a wide variety of otherpersistent conditions are known to be affected through the operation ofnervous tissue. For example, it is known that chronic hypertension thatmay not be responsive to medication may be improved or eliminated bydisabling excessive nerve activity proximate to the renal arteries. Itis also known that nervous tissue does not naturally possessregenerative characteristics. Therefore it may be possible tobeneficially affect excessive nerve activity by disrupting theconductive pathway of the nervous tissue. When disrupting nerveconductive pathways, it is particularly advantageous to avoid damage toneighboring nerves or organ tissue. The ability to direct and controlenergy dosage is well-suited to the treatment of nerve tissue. Whetherin a heating or ablating energy dosage, the precise control of energydelivery as described and disclosed herein may be directed to the nervetissue. Moreover, directed application of energy may suffice to target anerve without the need to be in exact contact, as would be required whenusing a typical ablation probe. For example, eccentric heating may beapplied at a temperature high enough to denature nerve tissue withoutcausing ablation and without requiring the piercing of luminal tissue.However, it may also be desirable to configure the energy deliverysurface of the present disclosure to pierce tissue and deliver ablatingenergy similar to an ablation probe with the exact energy dosage beingcontrolled by a power control and generation apparatus.

In some embodiments, efficacy of the denervation treatment can beassessed by measurement before, during, and/or after the treatment totailor one or more parameters of the treatment to the particular patientor to identify the need for additional treatments. For instance, adenervation system may include functionality for assessing whether atreatment has caused or is causing a reduction in neural activity in atarget or proximate tissue, which may provide feedback for adjustingparameters of the treatment or indicate the necessity for additionaltreatments.

Many of the devices and methods described herein are discussed relativeto renal nerve ablation and/or modulation. However, it is contemplatedthat the devices and methods may be used in other treatment locationsand/or applications where sympathetic nerve modulation and/or othertissue modulation including heating, activation, blocking, disrupting,or ablation are desired, such as, but not limited to: blood vessels,urinary vessels, or in other tissues via trocar and cannula access. Forexample, the devices and methods described herein can be applied tohyperplastic tissue ablation, cardiac ablation, pain management,pulmonary vein isolation, pulmonary vein ablation, tumor ablation,benign prostatic hyperplasia therapy, nerve excitation or blocking orablation, varicose veins, modulation of muscle activity, hyperthermia orother warming of tissues, etc. The disclosed methods and apparatus canbe applied to any relevant medical procedure, involving both human andnon-human subjects. The term modulation refers to ablation and othertechniques that may alter the function of affected nerves and othertissue.

FIG. 1 is a schematic view of an illustrative renal nerve ablationsystem 10 in situ.

In the illustrated embodiment, the system 10 is used to ablate one ormore renal nerves of a right kidney K. In the illustrated embodiment,only the right kidney K is shown for purposes of simplicity, however,the system 10 can be used for both right and left kidneys, andassociated renal vasculature, such as the renal artery RA that brancheslaterally from the abdominal aorta A.

In general, system 10 may include one or more conductive element(s) 18providing power to renal ablation system 12 disposed within a sheath 14,which is shown in more detail in subsequent figures. Although not shown,a proximal end of conductive element 18 may be connected to a controland power element(s) 16, which supplies the necessary electrical energyto activate one or more electrodes disposed at or near a distal end ofthe renal ablation system 10. The system 10 may further includeconnectors 20, 22 to electrically connect the conductive element(s) 18to the control and power element 16. The connector 20 may be designed soas to conform to the connector 22. For example, the connector 20 may bea male connector including a pin, whereas the connector 22 may be afemale connector with a hole to receive that pin. Other variations mayalso be contemplated. A connective link 24 such as a wire may connectthe connector 22 to the control and power element 16. The control andpower element 16 may include monitoring elements to monitor parameters,such as power, temperature, voltage, pulse size and/or shape and othersuitable parameters as well as suitable controls for performing thedesired procedure. The control and power element 16 may control a radiofrequency (RF) electrode. It is contemplated that any desired frequencyin the RF range may be used, for example, from 450-500 kHz. It is,however, contemplated that different types of energy outside the RFspectrum may be used as desired, for example, but not limited to,ultrasound, microwave, and laser technologies.

FIG. 2 illustrates a portion of an example renal nerve ablation device200 disposed within a lumen 206 of a vessel 204. In particular, thedevice 200 includes a catheter shaft 202 having an expandable member 210attached to a distal region 208 of the catheter shaft 202. In theillustrated embodiment, the expandable member 210 is a non-compliantballoon. The device 200 further includes two electrode assemblies 212 aand 212 b disposed on an external surface of the non-compliant balloon210.

Some blood vessels may have a generally tapered or narrowing shape.Because of this, during a medical procedure portions of thenon-compliant balloon 210 may contact the vessel wall, while otherportions, particularly, proximal portions, may be spaced from the vesselwall, thereby leading to mal-apposition of the non-compliant balloon 210at the proximal portion. In the areas, where the portions of thenon-compliant balloon 210 is in contact (e.g., narrowed areas), theremay be more expansion force on the vessel wall and this may sometimesdeform the vessel, thus, leading to stress induced trauma to the vessel204. In view of the above, the present disclosure discloses renalablation devices 300, 400, which will be discussed below in detail.

FIG. 3 illustrates an exemplary renal nerve ablation device 300. Therenal nerve ablation device 300 may include a catheter shaft 302 havingits distal region attached to an expandable member, such as a balloon304. In the illustrated embodiment, the balloon 304 may be a compliantballoon. Although not shown, a proximal region of the catheter shaft 302may extend proximally to remain outside of the patient's body. Thecatheter shaft 302 may also include one or more lumens extending betweenthe proximal and distal regions, where the catheter shaft 302 may beadapted to enter a patient's body. Specifically, the distal region ofthe catheter shaft 302 may be advanced within the patient's body toreach a target site. In certain instances, the proximal region of thecatheter shaft 302 may include a hub attached thereto for connecting toother diagnostic and/or treatment devices, which provides a port forfacilitating other interventions.

As shown, the catheter shaft 302 may be a tubular structure defining acircular cross-section. Those skilled in the art will appreciate thatother suitable cross-sections, such as rectangular, polygonal,irregular, etc., may also be contemplated. In addition, thecross-section of the catheter shaft 302 may be uniform along its lengthor may vary.

Materials employed to manufacture the compliant balloon 304 may includeany suitable biocompatible and compliant materials, such as, but are notlimited to, polymers such as low durometer Pebax, polyether block amide,polyurethane, silicone or the like. In at least some embodiments, theballoon material may match with material of electrodes pad 312(discussed below). In some embodiments, the thickness of the electrodespad 312 may be same or less than that of the compliant balloon 304. Inabove embodiments, the material employed may have an insulatingproperty, which may electrically isolate the catheter shaft 302 relativeto the compliant balloon 304 and/or to the bodily fluid. Materialsemployed to manufacture catheter shaft 302 may include polymers. Someexamples of suitable polymers may include polytetrafluoroethylene(PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylenepropylene (FEP), polyoxymethylene (POM, for example, DELRIN® availablefrom DuPont), polyether block ester, polyurethane (for example,Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC),polyether-ester (for example, ARNITEL® available from DSM EngineeringPlastics), ether or ester based copolymers (for example,butylene/poly(alkylene ether) phthalate and/or other polyesterelastomers such as HYTREL® available from DuPont), polyamide (forexample, DURETHAN® available from Bayer or CRISTAMID® available from ElfAtochem), elastomeric polyamides, block polyamide/ethers, polyetherblock amide (PEBA, for example available under the trade name PEBAX®),ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE),Marlex high-density polyethylene, Marlex low-density polyethylene,linear low density polyethylene (for example REXELL®), polyester,polybutylene terephthalate (PBT), polyethylene terephthalate (PET),polytrimethylene terephthalate, polyethylene naphthalate (PEN),polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI),polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (for example, KEVLAR®), polysulfone,nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon),perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin,polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof.

Further, the device 300 may include a flexible circuit assembly 306coupled to the compliant balloon 304. Flexible circuit assembly 306 mayinclude a semi- or compliant material such a PET/PEN with a printedconductive circuit (e.g., a metallic ink or carbon-based materials, suchas carbon nanotubes, graphene or nanobuds), whereby the conductivepathways are printed in a slightly meandering pattern allowing thecircuit pathways to be stretched. In some cases, the flexible circuitassembly 306 may be adhesively connected to the outer surface ofcompliant balloon 304. In particular, the flexible circuit assembly 306may be coupled to external surface of the compliant balloon 304, suchthat inflation of the compliant balloon 304 may stretch the flexiblecircuit 306 to conform to a vessel.

The flexible circuit 306 may include one or more pairs of bipolarelectrodes, such as bipolar electrode pairs 312 a and 312 d, 312 b and312 e, and 312 c and 312 f and in some embodiments, the electrode pairs312 a and 312 d, 312 b and 312 e, and 312 c and 312 f may be printed onthe compliant balloon 304. In some embodiments, the conductive pathwaysmay be directly printed on the compliant balloon surface, while a smallelectrode assembly is adhesively bonded to the balloon surface. Theprinted conductive pathways can be printed after assembling of theelectrode pads to the balloon surface, such they might run over theballoon surface as well as the electrode pads. This will allow forrelatively smaller electrode pads. Although three pairs of bipolarelectrodes are shown, but any suitable number of bipolar electrode pairsmay be employed, such as one, two, four, etc.

In general, the electrodes (312 a-312 f) may be printed on the flexiblecircuit assembly 306. For example, the flexible circuit 306/bipolarelectrodes 312 can be printed via inkjet and screen printing methods. Insome cases, the flexible circuit 306 may partially be printed electrodeson the compliant balloon 304 (e.g., flexible, printed electrodeassemblies).

Further, the flexible circuit 306 may include a set of thermistors 314 aand 314 b configured to measure the temperature at the electrodes site.The thermistors 314 a and 314 b may be employed to measure, or monitor,the temperature of the vessel wall, such as in real-time (i.e., duringthe renal ablation procedure, thus providing acute physician feedback).If the temperature crosses a set threshold, feedback may be provided tothe control and power element 16, which may automatically reduce thepower into the electrodes, as such avoiding a further rise or causing areduction of the temperature, in order to reduce or avoid incidence ofvessel trauma due to over-heating. For example, the control and powerelement 16 may decrease the amount of ablation energy, if thetemperature is too high. In another example, the control and powerelement 16 may increase the ablation energy, if the temperature becomestoo low. In addition, the thermistors 314 a and 314 b may measure thetemperature at the electrodes (312 a to 312 f).

The compliant balloon assembly may further include a set of pressuresensors 310 a and 310 b disposed along the compliant balloon 304, suchas at locations at or adjacent to the flexible circuit 306. The pressuresensors 310 a and 310 b may be configured to sense contact between anouter surface of the compliant balloon 304 and a target tissue (e.g.,via sensing increased resistance to further inflation). The sensedpressure may facilitate the operator in regulating inflation pressure ofthe compliant balloon 304, and thus the apposition of the flexiblecircuit 306. To this end, a controlled pressure may reduce or avoid anover-expansion of a vessel due to excessive applied pressure, therebyreducing or avoiding stress induced trauma to the vessel (as shown inFIG. 2).

In some embodiments, the device 300 may incorporate pressure-sensorfeedback mechanism for the operator to control inflation of thecompliant balloon 304, enhancing the operator's ability to inflate theballoon to a pressure in order to achieve the appropriate contact withthe vessel wall. For example, the pressure sensors 310 a, 310 b mayprovide real-time, acute feedback to the operator to stop or reduce theinflation if the pressure is too high. In another example, the pressuresensors 310 a, 310 b may also provide feedback in case that a portion ofthe compliant balloon 304 is not in contact with the vessel wall.

In some embodiments, the device 300 may incorporate pressure-sensorfeedback mechanism to be send to controller unit 16, which allows thecontroller unit 16 to automatically adjust the power level, pulse sizeand shape to each electrode pair based on one or more of the followingparameters: power level, temperature, pressure, and total ablation time.

In yet another embodiment, controller unit 16 may be designed toautomatically adjust, reduce, or increase the pressure level within theballoon to maintain adequate wall contact during the procedure.

In the illustrated embodiment, the pressure sensor 310 a may be disposedadjacent the proximal end region of the compliant balloon 304, whereasthe pressure sensor 310 b may be disposed adjacent to a distal endregion of the compliant balloon 304. In some embodiments, the device 300may include at least proximal pressure sensor such as pressure sensor310 a to sense whether the proximal part of the compliant balloon 304 isin contact with the vessel wall. Such an arrangement of the pressuresensors (310 a and 310 b) may facilitate real-time, acute measurement ofthe pressure over a wide length of the compliant balloon 304, and thusthe vessel, thereby enhancing accuracy of the procedure. Thisarrangement may also be useful when medical device 300 is utilized in atapered blood vessel because, for example, the proximal pressure sensor310 a can help to determine whether or not proximal portions of thecompliant balloon 304 are in contact with the blood vessel wall. Itshould be noted that any suitable number of pressure sensors includingone, three, four, etc., may be disposed in any suitable arrangementalong the flexible circuit 306, as desired.

Disposing the pressure sensor 310 a at or near the proximal end of thecompliant balloon 304 may also allow medical device 300 to have only asingle temperature sensor (e.g., one of the thermistors 314 a, 314 b).This may be because, for example, the compliant balloon 304 may conformwith substantially equal pressure along the vessel wall, such thatmeasuring the contact pressure at just one point, will provide knowledgeabout the conformability of the entire balloon surface.

The pressure sensors 310 a and 310 b may be any suitable sensor, such asa polyethylene terephthalate foil pressure sensor. Other pressuresensors are contemplated.

Although a single flexible circuit 306 is shown, it should be noted thatany suitable number of flexible circuits may be employed including two,three, four, etc. Further, one or more flexible circuits 306 may bepositioned in any suitable arrangement along the external surface of thecompliant balloon 304. In general, the flexible circuit(s) 306 can bearranged along the external surface of the compliant balloon 304 toattain desired lesion pattern(s). Exemplary lesion patterns, and thusthe arrangement of the flexible circuits 306, may be helical along thelongitudinal length of the compliant balloon 304.

FIG. 4 illustrates another exemplary renal nerve ablation device 400.The device 400 may include a catheter shaft 402 having an expandablemember 404 attached to its distal region. The expandable member 404 mayinclude a compliant balloon having a structure and function similar tothat of the compliant balloon 304 of FIG. 3. Similarly, the cathetershaft 402 also has a structure and function similar to that of thecatheter shaft 302 of FIG. 3.

The device 400 may further include a flexible circuit assembly 406coupled to an external surface of the compliant balloon 404. In somecases, the flexible circuit assembly 406 may be adhesively ormechanically coupled on the compliant balloon 404. The flexible circuit406 may include one or more electrode pads, each having one or morepairs of bipolar electrodes. For example, a first electrode pad mayinclude three bipolar electrode pairs 412 a and 412 d, 412 b and 412 e,and 412 c and 412 f (collectively 412). Similarly, a second electrodepad, which may be separated to the first electrode pad by a distance,may include another three bipolar electrode pairs 416 a and 416 d, 416 band 416 e, and 416 c and 416 f (collectively 416). In some embodiments,these electrode pairs 412, 416 may be printed on the compliant balloon404. Although each of these electrode pads includes three pairs ofbipolar electrodes, but any suitable number of bipolar electrode pairsmay be employed, such as one, two, four, etc.

In general, the electrode pairs 412, 416 may be printed on the flexiblecircuit 406 using known, related art, or later developed printingmethods, including, but not limited to, inkjet and screen printingmethods. In some embodiments, the flexible circuit 406 may be thin filmpads.

Further, the flexible circuit 406 may include three thermistors 414 a,414 b, and 414 c configured to measure the temperature at the electrodessite. In particular, thermistor 414 a may be placed adjacent the firstelectrode pad, thermistor 414 c may be placed adjacent the secondelectrode pad, and thermistor 414 b may be placed in between the firstand second electrode pad. Each thermistor (414 a, 414 b, and 414 c;collectively 414) may be employed to measure the temperature of thevessel wall, such as in real-time (i.e., during the renal ablationprocedure). If the temperature crosses a set threshold, feedback may beprovided to the control and power element 16, which may automaticallychange the temperature. This temperature control may reduce or avoidincidence of vessel trauma due to over-heating. In addition, thethermistors 414 may measure the temperature of flexible circuit 406,which may reduce or avoid fouling of electrodes during the ablationprocedure.

The flexible circuit 406 may further include a set of pressure sensors410 a and 410 b (collectively 410) disposed along the compliant balloon404, while positioned at or adjacent to the flexible circuit 406. Thepressure sensors 410 a and 410 b may be configured to sense contactbetween an outer surface of the compliant balloon 404 and a targettissue. The sensed pressure may facilitate the operator in regulatingthe inflation of the compliant balloon 404, and thus the apposition ofthe flexible circuit 406. To this end, a controlled pressure may reduceor avoid an over-expansion of a vessel due to excessive appliedpressure, thereby reducing or avoiding stress induced trauma to thevessel (as shown in FIG. 2)

Similar to the above embodiments, the two pressure sensors 410 a and 410b may be disposed at or adjacent the proximal and distal end regions ofthe compliant balloon 404, respectively. In some embodiments, the device400 may include at least proximal pressure sensor such as pressuresensor 410 a to sense whether the proximal part of the compliant balloon404 is in contact with the vessel wall. Such an arrangement of thepressure sensors 410 may facilitate real-time, acute measurement of thepressure over a wide length of the compliant balloon 404, and thus thevessel, thereby enhancing accuracy of the procedure. It should be notedthat any suitable number of pressure sensors, including one, three,four, etc., may be disposed in any suitable arrangement along theflexible circuit 406, as desired.

In some embodiments, the device 400 may incorporate pressure-sensorfeedback mechanism for the operator to control inflation of thecompliant balloon 404, enhancing the operator's ability to inflate thecompliant balloon 404 to a pressure in order to achieve the appropriatecontact with the vessel wall. For example, the pressure sensors 410 a,410 b may provide real-time, acute feedback to the operator to stop orreduce the inflation if the pressure is too high. In another example,the pressure sensors 410 a, 410 b may also provide feedback in case thecompliant balloon 404, or a portion thereof, is not in contact with thevessel wall.

The pressure sensors 410 a and 410 b may be any suitable sensor, such asa polyethylene terephthalate foil pressure sensor. Other suitable known,related art, or later developed pressure sensors may also be employed,without departing from the scope and spirit of the present disclosure.

In some embodiments, the flexible circuit 406 may be helically disposedabout the longitudinal axis of the catheter shaft 402. The flexiblecircuit 406 shown may be disposed at an angle relative to thelongitudinal axis of the catheter shaft 402. Angling the flexiblecircuit 406 may help withdrawing the catheter shaft 402 into a guidecatheter.

An exemplary method of ablating renal nerves can utilize either device300 or 400 (as shown in FIGS. 3-4, respectively). The device 300 may beadvanced through a blood vessel to a position within a renal artery.Subsequently, an operator may inflate the device 300 to expand thecompliant balloon (i.e., the expandable balloon 304 of FIG. 3). In theexpanded position, the electrodes may come into contact with the vessel,and the pressure between the compliant balloon and the renal artery canbe sensed using the pressure sensor 410 a, for example. Once a desiredpressure is attained, one or more pairs of bipolar electrodes may beactivated to ablate the surrounding renal nerves and/or tissue.

Although the embodiments described above have been set out in connectionwith a renal nerve ablation device, those of skill in the art willunderstand that the principles set out there can be applied to anydevice where it is deemed advantageous to provide flexibility to therenal nerve ablation device. Conversely, constructional details,including manufacturing techniques and materials, are well within theunderstanding of those of skill in the art and have not been set out inany detail here. These and other modifications and variations are wellwithin the scope of the present disclosure and can be envisioned andimplemented by those of skill in the art.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the embodiments disclosed herein. It is intended that thespecification and examples be considered as exemplary only, anddeparture in form and detail may be made without departing from thescope and spirit of the present disclosure as described in the followingclaims.

What is claimed is:
 1. A medical device for ablation, comprising: acatheter shaft having a distal region; an expandable member coupled tothe distal region; a flexible circuit assembly coupled to the expandablemember, the flexible circuit assembly comprising first and secondbipolar electrode pairs, a first temperature sensor between electrodesof said first bipolar electrode pair, a second temperature sensorbetween electrodes of said second bipolar electrode pair, and a thirdtemperature sensor between said first and second bipolar electrodepairs; a plurality of pressure sensors disposed at an outer surface ofthe expandable member along a length of the expandable member, theplurality of pressure sensors comprising a first pressure sensorpositioned only at a proximal end of the expandable member and a secondpressure sensor positioned only at a distal end of the expandablemember, each of the plurality of pressure sensors being configured tosense contact between the outer surface of the expandable member and atarget tissue; a controller unit, wherein the controller unit isconfigured to automatically adjust the power level to each of the firstand second bipolar electrode pairs based on feedback from the pluralityof pressure sensors; and a pressure-sensor feedback mechanism that usespressure sensed by the pressure sensors to allow the controller unit toautomatically adjust a pressure level within the expandable member tomaintain the contact between the outer surface of the expandable memberand the target tissue during a procedure.
 2. The medical device of claim1, wherein the expandable member includes a compliant balloon.
 3. Themedical device of claim 2, wherein the compliant balloon includespolyether block amide.
 4. The medical device of claim 2, wherein thecompliant balloon includes polyurethane.
 5. The medical device of claim1, wherein the flexible circuit assembly includes one or more additionaltemperature sensors.
 6. The medical device of claim 1, wherein thecatheter shaft has a longitudinal axis and wherein at least a portion ofthe flexible circuit assembly is disposed at an angle relative to thelongitudinal axis.
 7. The medical device of claim 1, wherein thecatheter shaft has a longitudinal axis and wherein at least a portion ofthe flexible circuit assembly is helically disposed about thelongitudinal axis.
 8. The medical device of claim 1, wherein theflexible circuit assembly includes one or more printed electrode pads.9. The medical device of claim 1, wherein the plurality of pressuresensors each includes a polyethylene terephthalate foil pressure sensor.10. A medical device for ablation, comprising: a catheter shaft having adistal region; a compliant balloon coupled to the distal region; one ormore pairs of bipolar electrodes coupled to the compliant balloon; oneor more temperature sensors coupled to the compliant balloon; aplurality of pressure sensors coupled to the compliant balloon anddisposed at an outer surface of the balloon along a length of theballoon, the plurality of pressure sensors comprising a first pressuresensor positioned only at a proximal end of the expandable member and asecond pressure sensor positioned only at a distal end of the expandablemember, each of the plurality of pressure sensors being configured tosense contact between the outer surface of the balloon and a targettissue; a controller unit, wherein the controller unit is configured toautomatically adjust the power level to each of the one or more pairs ofbipolar electrodes based on feedback from the plurality of pressuresensors; and a pressure-sensor feedback mechanism that uses pressuresensed by the plurality of pressure sensors to allow the controller unitto automatically adjust a pressure level within the balloon to maintainthe contact between the outer surface of the expandable member and thetarget tissue during a procedure.
 11. The medical device of claim 10,wherein the one or more pairs of bipolar electrodes are disposed along aflexible circuit coupled to the compliant balloon.
 12. The medicaldevice of claim 11, wherein the catheter shaft has a longitudinal axisand wherein at least a portion of the flexible circuit is disposed at anangle relative to the longitudinal axis.
 13. The medical device of claim11, wherein the catheter shaft has a longitudinal axis and wherein atleast a portion of the flexible circuit is helically disposed about thelongitudinal axis.
 14. The medical device of claim 10, wherein at leastone of the plurality of pressure sensors are disposed adjacent to aproximal end region of the compliant balloon.
 15. The medical device ofclaim 10, comprising one of the plurality of pressure sensors positionedbetween one of the one or more pairs of bipolar electrodes.
 16. A methodfor ablating nerves, the method comprising: advancing a medical devicein accordance with claim 10 through a blood vessel to a position withinan artery; expanding the compliant balloon; sensing contact between thecompliant balloon and the artery with the plurality of pressure sensors;and activating at least one of the one or more pairs of bipolarelectrodes.